U.S. and British planes patrolling a no-fly zone over northern Iraq bombed Iraqi air defense systems Monday in response to anti-aircraft fire, U.S. officials said.

It was the first time U.S. and British planes had bombed Iraq's north since the Sept. 11 terrorist attacks, said Capt. Brian Cullin, a spokesman for U.S. European Command in Stuttgart, Germany. The bombing came amid a rising debate on whether Iraq will be the next target of the U.S. anti-terror campaign.

The bombs were dropped after Iraqi forces northeast of Mosul in northern Iraq fired on a routine air patrol, the U.S. European Command said in a written statement.

"All coalition aircraft departed the area safely," the statement said. Cullin said it would not be clear for some time how much damage was done to the Iraqi targets.

U.S. and British planes based in southeast Turkey have been flying patrols over northern Iraq since September, 1996. The two countries say the operation is designed to protect the Kurdish population of northern Iraq from Iraqi leader Saddam Hussein.

"There's a day-to-day commitment made by three very strong coalition partners ... toward a population we still feel we have an obligation to protect," Cullin said.

Expectations that Iraq could be the next target of the U.S.-led anti-terror campaign were strengthened by President Bush's State of the Union address last week.

Bush said Iraq was part of an "axis of evil," along with Iran and North Korea, and accused it of seeking weapons of mass destruction.

Turkey, host to the air patrols and a launching pad for strikes against Iraq in the 1991 Gulf War, has expressed anxiety over the prospect of war in Iraq, fearing that the fall of the Baghdad regime could lead Kurds in northern Iraq to create a Kurdish state. That could in turn boost aspirations of autonomy-seeking Kurds in Turkey.

Turkey's Prime Minister, Bulent Ecevit, warned Iraq on Monday to admit U.N. weapons inspectors in order to head off possible U.S. military action.

Iraq has refused since 1998 to allow U.N. inspectors into the country to check if the Baghdad regime has dismantled its weapons of mass destruction. Baghdad has rejected a U.S. warning to admit the inspectors or face the consequences.